1. Field of the Invention
The present invention relates to a circuit module and, in particular, to a circuit module comprised in a carrier and decks of circuit chips arranged on the carrier, wherein the circuit chips are grouped in different groups which are active at different times.
2. Description of the Invention
A conventional structure of memory modules, DIMMs (DIMM=Dual In-Line Memory Module), for example, includes a module board and groups of memory chips, DRAM chips, for example, arranged on the module board. In high-density memory modules, the memory chips are stacked on the module board, wherein each stack contains multiple memory chips stacked on top of each other. Usually, each stack comprises two memory chips, one arranged in a first layer and one arranged in a second layer of the stack.
In such a prior art memory module, the memory chips are grouped into two banks of memory chips, wherein only one bank of memory chips is active at a time. The memory chips of the active bank are selected by way of a bank select signal. In the above prior art memory module, the arrangement of the memory chips is such that the memory chips belonging to a first bank are arranged in the first layer (the bottom layer, for example) of the stacks of memory chips, whereas the memory chips belonging to the second bank are arranged in the second layer (the top layer, for example) of the stacks of memory chips.
The power dissipation in such high-density memory modules is very high. The arrangement of the memory chips explained above, wherein memory chips belonging to the same memory bank are arranged in the same layer, the dissipation of heat is difficult. Thus, the temperature of the memory module can reach 80° C. to 90° C. Especially, if the bank of the bottom chips is active, the heat convection to the surrounding air is very bad. This may result in a breakdown of memory chips and, therefore, of the memory module.